Dyeing of polyacrylonitrile fibers



Patented Sept. 22, 1953 nyemo or POLYACRYLONITRILE FIBERS Robert H. Blaker, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wil- I mington, DeL, a corporation of Delaware No Drawing. Application May 24, 1951, Serial No. 228,109

7 Claims.

1 This invention relates to the dyeing 01' polyacrylonitrile fibers, and more particularly to the dyeing of fibers in which the polymer contains at least 40% acrylonitrile, with dyes of the class generally known as acid wool dyes and direct dyes in the presence of a copper salt and hydroxylamine.

Due to the inherent characteristic of polyacrylonitrile fibers, great difiiculty has been experienced in dyeing these fibers by any of the known methods, and up to the present tim the most satisfactory method for dyeing these particular fibers has been with the aid of cuprous salts generally referred to as the cuprous ion technique, as more particularly disclosed in Chemical and Engineering News 28, 4268 (1950) and in the pamphlet entitled Dyeing and Wet Finishing Technique for Dynel published by Union Carbide and Carbon Corporation in July 1950. In the so-called cuprous ion technique, the dyes are applied from an aqueous solution containing cuprous ions produced from cupric salts by means of sodium formaldehyde-sulfoxylate r zinc formaldehyde-sulfoxylate. In this method it has been difiicult, and in most cases impossible, to prevent the precipitation of metallic copper, especially when short baths are-used, that is, where the ratio of the weight of dye bath to the weight of the fiber is 10:1 to 20:1. Even when longer baths are employed the cuprous ion is oxidized by the oxygen of the air to the cupric ion (which is ineffective for dyeing), and attempts to reduce the cupric ion to the cuprous ion directly in the dye bath have been unsuccessful.

It is an object of the present invention to provide a method for dyeing polyacrylonitrile fibers, including cc-polymers, with acid and direct dyes in which the precipitation of metallic copper is avoided and strong, level dyeings of good fastness properties are obtained. A more specific object of the invention is to provide a method for applying acid and direct colors to polyacrylonitrile fibers in a dye bath in which suflicient cuprous ions are available to effect the dyeing of the fiber without reduction of the dye and without permitting disproportionation of cuprous ions to cupric ions and metallic copper by a process in which it is assumed that the cuprous ions are combined with the reducing agent or its oxidation products, or both.

I have found that polyacrylonitrile fibers can be dyed in strong, level shades from aqueous baths at a pH of 1.5 to 5 in the presence of copper salts in amounts sufficient to provide 0.25 to 3.0 weight per cent of cuprous ion and from 0.15 to 3.2 weight per cent of hydroxylamine (both based on the weight of the fiber to be dyed) where the dyeing is effected at temperatures of 190 to 250 F.

By polyacrylonitrile textile materials we mean staple, raw stock and tow, as well as filament, fiber stock and fabric. These may be composed of acrylonitrile homo-polymer (see U. S. Patent 2,436,926), or modified polyacrylonitrile such as c-opolymers with up to 15% of vinyl pyridine or methyl vinyl pyridine, or up to of vinyl chloride. The polyacrylonitrile may also be mixed with other materials such as plasticizers, modifiers, etc. (see U. S. Patent 2,491,471). The acid and direct colors which are particularly suitable for use in the present process are those which contain acid groups such as -SO3H, -COOH, OSO:H. Th term acid colors" is used to designate the commonly known group of compounds useful for the dyeing of wool, while the term direct colors" is used to designate those dyes which usually contain acid groups as stated above but are employed in the dyeing of cellulose material.

Metallized dyes are also useful. In the case of metallizable acid colors with th 0-, o'-dihydroxy azo grouping, the cupric complexes are formed in this dyeing process.

The dyeing is'carried out preferably at a pH of 1.5 to 5. At the lower pH range brighter dyeings are obtained, although at a slower rate than when a higher pH range is employed. A buffer, such as sodium diacid phosphate, may be employed with advantage.

The cuprous ion may be formed in situ or added in the form of a cuprous salt, but in either case the specified amount of the hydroxylamin is operable.

This process is applicable to the dyeing of polyacrylonitrile fibers by any of th usual processes, including package dyeing, padding, and printing.

The dyeing may be carried out at temperatures of from to 250 F., although temperatures of from 200 to 215 F. are usually employed.

The hydroxylamine may be used as the free base or in the form of its various known salts such as the sulfate, acid sulfate, and chloride. The sulfates ar preferred, since the chlorides present corrosion difficulties in the usual equipment.

For light shades the smaller amounts of copper and hydroxylamlne are used, while for heavy shades the higher amounts of both are required. Moreover, the heavy shades require a longer dyeing cycle than do light shades. Since the presaesaon 3 ence of large amounts of copper in theflnished dyeings render the fiber less stable to heat,-it is desirable to use as small an amount of copper a practical to attain the desired strength of dyeing.

Dyeing assistants such as benzoic acid or pphenyl phenol may be used to increase the rate of dyeing.

This method permits commercially acceptable dyeing of polyacrylonitrile materials in a ,wide variety of shades with good fastness. A particular advantage is that this is accomplished without precipitation of metallic copper and without corrosion of type 304 stainless steel which is widely used in textile dyeing equipment. Furthermore, the process is operable in both long and short baths, which makes the method adaptable to various types of equipment usually available in textile dyeing establishments.

The following examples are given to illustrate the invention and to show various modifications of procedure that may be employed, but it is to be understood that the invention is not limited to the particular dyes, procedure or methods of application illustrated but is applicable to the dyeing of polyacrylonitrile fibers either as homopolymers or as copolymers in which the acrylonitrile units constitute a substantial portion of the polymer. In these examples the polyacrylonitrile, unless otherwise designated, is the homopolymer either as a staple or continuous filament yarn drawn from four to eight times its original spun length. In all cases the amount of dye employed is given in per cent based on the Percent Example Dye of D" Color The dye of O. I. 833 0. 5 Bright blue. The dye of O. I. 15 0.8 Orange.

8 The dye ol 0. I. 169.....L... 0.3 Blue-red.

4 Yellow dye of Example 1 of 0.3 Yellow.

British Patent 466,799.

6 The dye of O. I. 801 0. 9 Bright greenyellow.

6 The dye of C. I. 40 1.2 Orange.

7 The dye of O. I. 36 l. Dull yellow.

8 Anthranilic acid 7- 1. Brown.

anilino-l-naphthol-B-sulionic acid.

9 Orange dye of 4-nitro2-am- 1.6 Orange.

inophenol l-(4- suiioPhenylwmethyl-li-pymo one, coppered.

Example 10 To 12.5 parts of water was added 0.125 part of cupric sulfate, 0.05 part of hydroxylamine sul- Example 11 To 200 parts of water was added 0.10 part each of copper sulfate and hydroxylamine sulfate, 5 parts of polyacrylonitrile staple fabric 4 and 1% of the dye of C. I. 176 based on the weight of the fiber. The dyeing was maintained at the boil for 1.5 hours. A red dyeing was obtained.

Example 12 1 To 100 parts of water was added 0.16 part each of copper sulfate and hydroxylamine sulfate, 2.5 parts of polyacrylonitrile continuous filament fabric and 1% of the blue dye 1-amino-2-sulfo- 4-anilino-anthraquinone, based on the weight of the fabric. The dyeing was continued at the boil for 4 hours. A blue dyeing was obtained.

Example 13 To 100 parts of water was added 0.125 part of copper sulfate and 0.12 part of hydroxylamine sulfate, 2.5 parts of polyacrylonitrile staple with 1% of the blue dye l-amino-2-sulfo-4-anilinoanthraquinone, based on the weight of the fiber. The dyeing was boiled at reflux for 3 hours to give a bright blue dyeing.

Example 14 To 2.5 parts of polyacrylonitrile staple, 0.125 part of cupric sulfate and 0.042 part of hydroxylamine hydrochloride and 100 parts of water, was added 1% of the blue dye 1-amino-2-sulfo-4- anilino-anthraquinone, based on the weight of the fiber, and dyeing continued at boil for 1 hour. A blue dyeing was obtained.

Example 15 part of cuprous chloride, 0.038 part of hydroxylamine sulfate in a volume of 25 parts of water was added 1% of the dye of C. I. 176. The dye bath was boiled one-half hour. A red dyeing was obtained Examples 16 and 17 conditions, a blue dyeing was obtained in 5 minutes.

Examples 18 and 19 A polyacrylonitrile staple prepared according to Example 5 of U. S. Patent 2,491,471, in which 5% of 2-methyl-5-vinyl pyridine was employed, dyed b the method of Example 16 with the dye of C. I. 1'76, gave a strong red dyeing in one-half hour. Using 1% of the blue dye 1-amino-2-sulfo- 4-anilino-anthraquinone, a blue dyeing was obtained in 15 minutes.

Examples 20 and 21 Dyne1," a staple fiber comprising a co-polymer of about 60% of vinyl chloride and 40% of acrylonitrile, when dyed by the procedure of Example 16 gave a red dyeing with 2% of the dye of C. I: 176, and 15 minutes. Using 1% of the blue dye 1-amino-2-sulfo-4-anilino-anthraquinone, a blue dyeing was obtained in 10 minutes.

Examples 22 and 23 Chemstrand, a staple fiber comprising a 3- component polymer containing about acrylonitrile, when dyed by the process of Example 16 gave a strong red dyeing in 25 minutes with tained.

the dye of C. I. 176, and a strong blue dyeing witlr: the blue dye 1-amino-2-sulfo-4-anilino-anthraquinone in minutes.

In Examples 24 to 40 as listed below, the dyeings wereprepared by adding 2.5 parts of polyacrylonitrile staple, 0.125 part of cupric sulfate, 0.05 part ofhydroxylamlne sulfate, to 100 parts of water. The amount of dye designated in the following table was then added and the dyeing was carried out at 250 F. for one hour in a closed vessel. Strong dyeings of the colors given were obtained.

Example Dye 3 33 Color 24 The dye of O. I. 1078 1. 2 Green. 25 Orange dye of Example 2 of 0.8 Orange.

U. S. Patent 1,623,005.

833 1.0 Blue.

0.6 Blue-red. ye of 0. I. 639 1.8 Yellow. 4,4-diamino-1,l-diantbrimide- 1.0 Blue-gray.

2,2-disulionic acid. 4-cbloro-2-aminophenol-d-sul- 1.0 Violet.

ionic-acid 8-acetamido-2-naphthol. 3i The dye of C. I. 365 1.6 Redellow. 32 The dye of C. I. 252 1.8 Redrown. 33 4-nitro-2-aminophenol 1.6 Orange.

:(4'-su1f{ phenyl)-3-mighylazo one. co pere 34 Dla i s idine (2-naph- 0.5 Violet.

thol-d-sulionic acid); coppered as in U. 8. Patent 2,437,699. 35 2-aminophenol-4-sulionic acid 2 Blue-red.

2-naphthol, coppcred as in Swiss Patent 79,654. 36 Dye of Example 8 l. 5 Brown. 37 (2-aminophenol-i-suliona- 0.8 Red.

mide 2-naphthol)cobaited.

38 Red dye of Example 1 of 0.8 Red.

British Patent 637,665. 39 Picramic acid 8- 0.8 Blue-gray.

amino-1-naphthol-3,6-disulionic acid. 40 The dye of C. I. 246 l. 6 Green-gray.

Example 41 Into a 1 lb. Smith-Drum circulating package dyeing machine was charged 400 g. of polyacrylonitrile staple raw stock, 4000 cc. of water was added and circulated followed by the addition of 10 g. of cupric sulfate, 4 g. of hydroxylamine sulfate, 0.4% naphthoquinophthalone, 0.60% of the orange dye C. I. 15, and 0.68% of the. blue dye l-amino-2-sulfo-4-anilino anthraquinone, to give approximately 4800 cc. total machine volume. The temperature was increased to' 200 and maintained atthat point for 1 hour. The bath was dropped and the polyacrylonitrile fiber secured with a long chain alcohol sulfate in concentrations of 1 g. per liter at 160 F. for 15 minutes. The dyeing obtained was olive drab, with excellent color penetration and equalization throughout.

Example 42 anthraquinone, in approximately 4800 cc. of,

water, was heated to 206 F. and maintained at that point for 1 hours. The dyeing obtained was scoured as above and a navy blue shade of excellent penetration and equalization was ob- Example 43 A chocolate brown was obtained in a similar fashion as the Example 42 by use of 40 g. of

6 cupric sulfate, 32 g. of hydroxylamine sulfate. 40 g. of NaHzPO4, 6.8 g. of the orange dye of C. I. 161, 7.2 g. of the blue dye 1-amino-2-sulfo-4- anilino-anthraquinone, 4.0 g. of the yellow dye 4' nitro 2'-su1fo-4-amino-diphenylamine- 2- cresol, tosylated, and 2.6 g. of the red dye of C. I.

176. The dyeing had excellent penetration and equalization.

Example 44 Examples 45 and 46 A thickener was made up of 71 parts of starchtragacanth paste. 4 parts of hydroxylamine sulfate, 16 parts of 25% solution of cupric sulfate and 9 parts of water. A printing paste was made up with 1 part color, 35 parts of water, 4 parts of glycerine and 60parts of the above thickener. Prints were made with this printing paste on polyacrylonitrile staple fabric, dried and then aged in a Cottage steamer at 3 to 4 lbs. steam pressure for 1 hour. The prints were rinsed and soaped at 160 F. and dried. With the blue dye l amino 2 sulfo 4 aniline anthraquinone, a pleasing blue was obtained, and with the red dye of C. I. 176 a red was obtained.

Example 47 To 2.5 parts of Dynel (as identified above) in skein form in cc. of water, were added 0.125 part of cupric sulfate. 0.05 part of hydroxylamine sulfate and 0.05 part of dye, 5-nitro 2 aminophenola 1 phenyl 3 methyl 5- pyrazolone chromed, and the dyeing was carried out for 1.3 hours at the boil. A blue-red dyeing was obtained.

As illustrated in the above examples, the hydroxylamine is preferably added as the readily available sulfate, although, if desired, the hydroxylamine base of course can be employed since it is converted to the salt on adjustment of the dye bath to the pH required in the dyeing process.

Ordinarily, where hydroxylamine sulfate as such is employed, the pH of the dye bath would fall within the specified range of 1.5 to 5. Where a. hydroxylamine acid sulfate of commerce is employed, the vpH will usually require adjustment by the addition of alkalies, preferably alkaline salts which in their addition do not cause precipitation of basic salts of copper due to local concentration of hydroxyl ions. In short volumes even where hydroxylamine sulfate is employed, due to the reaction of the copper salt and hydroxylamine the pH may fall below 1.5, in which case it will be necessary, prior to the addition of the color, to add alkaline salts to bring the pH up within the range specified.

By the process as described, dyeings of substantially any strength desired may be obtained, from pale shades to very dark shades, including black. In the dyeing of the polyacrylonitrile fibers which have been drawn to a high degree, more dye is required to attain the same depth of shade, but by this process even the highly drawn fibers may be dyed in deep shades.

By the process above described. dyeings may 7 be produced with acid and direct dyes in short as well as long baths without encountering precipitation of metallic copper or undue destruction of the dye by means oi the reducing agent employed.

I claim:

1, A process for dyeing a fiber produced from a material from the class consisting of polyacrylonitrile and copolymers of acrylonitrile containing at least 40% acrylonitrile with a dye from the class consisting 01' an acid dye and a direct dye which comprises applying the dye in an aqueous medium having a pH of from 1.5 to 5 containing a copper salt in an amount sufficient to provide 0.25 to 3.0 weight percent of cuprous ion, and from 0.15 to 3.2 weight percent of hydroxylamine, both based on the weight of the material to be dyed, and carrying out the dyeing at temperatures of from 190 to 250 F.

2. A process for dyeing a fiber produced from a. material from the class consisting of polyacrylonitrile and copolymers oi acrylonitrile containing at least 40% acrylonitrile with a dye from the class consisting of an acid dye and a direct dye which comprises carrying out the dyeing in an aqueous bath having a pH of from 1.5 to 5 and which contains a copper salt in an amount sufiicient to provide 0.25 to 3.0 weight percent oi cuprous ion, and from 0.15 to 3.2 weight persuilieient to provide 0.25 to 8.0 weight percent of cuprous ion, and i'rom 0.15 to 3.2 weight percent 01 hydroxyiamine in the form oi. a hydroxylamine sulfate. both based on the weight of the material to be dyed, and carrying out the dyeing at temperatures of from to 250 F.

4. The process of claim 2 wherein the dyeing is carried out at a temperature of about 212 F.

5. The process of claim 3 wherein the dyeing is carried out at a temperature of about 212 F.

6. A process for dyeing a fiber produced from a material irom the class consisting of polyacrylonitrile andv copolymers of acrylonitrile containing at least 40% acrylonitrile with a dye from the class consisting of an acid dye and a direct dye which comprises carrying out the dyeing in an aqueous bath of short volume having a pH of from 1.5 to 5 and which contains a copper salt in an amount sumcient to provide 0.25 to 3.0 weight per cent of cuprous ion, and from 0.15 to 3.2 weight per cent of hydroxylamine, both based on the weight of the material to be dyed. and carrying out the dyeing at temperatures of from 190 to 250 F.

'7. The process of claim 6 wherein the dyeing is carried out at a temperature of about 212 F.

ROBERT H. BLAKE'R.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Straub Feb. 28. 1939 OTHER REFERENCES Number 

1. A PROCESS FOR DYEING A FIBER PRDUCED FROM A MATERIAL FROM THE CLASS CONSISTING OF POLYACRYLONITRILE AND COPOLYMERS OF ACRYLONITRILE CONTAINING AT LAST 40% ACRYLONITRILE WITH A DYE FROM THE CLASS CONSISTING OF AN ACID DYE AND A DIRECT DYE WHICH COMPRISES APPLYING THE DYE IN AN AQUEOUS MEDIUM HAVING A PH OF FROM 1.5 TO 5 CONTAINING A COPPER IN AN AMOUNT SUFFICIENT TO PROVIDE 0.25 TO 3.0 WEIGHT PERCENT OF CUPROUS ION, AND FROM 0.15 TO 3.2 WEIGHT PERCENT OF HYDROXYLAMINE, BOTH BASED ON THE WEIGHT OF THE MATERIAL TO BE DYED, AND CARRYING OUT THE DYEING AT TEMPERATURES OF FROM 190* TO 250* F. 